Status Epilepticus (SE) is a major neurological emergency affecting over 150,000 people/year in the US. Despite advances in treatment strategies, SE is still associated with a significant level of mortality. It has been well- established that a significant number of SE patients respond poorly to treatment. These resistant patients have a much higher mortality rate than patients than respond rapidly to treatment. Therefore, understanding the cellular and molecular mechanisms that result in decreased responsiveness to therapy is essential to develop intervention strategies to better treat this life-threatening condition. SE has been shown to alter GABA/ AR function in a duration-dependent manner. This acute and progressive alteration of GABA/AR function has been attributed to a post-translational modification of the receptor. A significant inhibition of CaM kinase II activity has been observed in multiple animal and in vitro models of SE. In addition, CaM kinase II has been shown to augment GABA/AR function. SE-induced inhibition of CaM kinase II results in decreased GABA/AR sub-unit phosphorylation. This observation has led us to develop the CENTAL HYPOTHESIS that GABAergic inhibition progressively decreases as SE duration increases due in part to alteration in phosphorylation of GABA/AR subunits by CaM kinase II and this may contribute to the induction of BZ resistance and intractability to treatment in prolonged SE. The experimental aims will utilize two well characterized models of SE: The experimental aims will utilize two well characterized models of SE: The rat pilocarpine model (pilo-SE) and the hippocampal neuronal culture model (HNC-SE). Both models of SE show a loss of BZ sensitivity in a duration-dependent manner. Therefore, these models will be utilized to elucidate the cellular and molecular mechanism which result in SE duration-dependent decrease in GABA/AR function, and accomplish the following specific aims: 1) Characterize the effect of SE duration on agonist and allosteric modulator binding and GABA/AR function. 2) Determine the effect of SE duration on CaM kinase II activity and GABA/AR subunit phosphorylation, and 3) Examine whether CaM kinase II-dependent phosphorylation of the GABA/AR alters agonist and allosteric modulator binding and GABA/AR function. Accomplishment of these specific aims will significantly advance our understanding of BZ resistant in SE. Since BZ intervention is the front line therapy for SE patients, understanding the cellular and molecular mechanisms which result in the development of BZ resistance in SE is essential for advancing the clinical management of this neurological emergency. The significance of this research proposal is that it describes a molecular mechanism whereby prolonged seizure activity modulates the function of a major neurotransmitter receptor complex. Understanding the cellular mechanisms that result in altered GABA/AR function in SE is essential to the development of new treatment strategies to manage SE in the clinical setting.